Papers by Matthew W Turnbull
Proceedings of the Entomological Society of Washington, 2014
Journal of Insect Science, 2011
Recent studies have demonstrated that hemichannels, which form gap junctions when paired from app... more Recent studies have demonstrated that hemichannels, which form gap junctions when paired from apposing cells, may serve additional roles when unpaired including cell adhesion and paracrine communication. Hemichannels in mammals are formed by connexins or pannexins, while in insects they are formed by pannexin homologues termed innexins. The formation of functional gap junctions by insect innexins has been established, although their ability to form functional nonjunctional hemichannels has not been reported. Here the characteristics of nonjunctional hemichannels were examined in three lepidopteran cell types, two cell lines (High Five and Sf9) and explanted hemocytes from Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae). Selective fluorescent dye uptake by hemichannels was observed in a significant minority of cells, using fluorescence microscopy and flow cytometry. Carbenoxelone, an inhibitor of mammalian junctions, disrupted dye uptake, while flufenamic acid and mefloquine did not. The presence of Ca 2+ and Mg 2+ in the media increased hemichannel activity. Additionally, lipopolysaccharide, a stimulator of immune activity in lepidopterans, decreased dye uptake. These results demonstrate for the first time the activity of nonjunctional hemichannels in insect cells, as well as pharmacological tools to manipulate them. These results will facilitate the further examination of the role of innexins and nonjunctional hemichannels in insect cell biology, including paracrine signaling, and comparative studies of mammalian pannexins and insect innexins.
Journal of Insect Science, 2004
Endoparasitoids of arthropods evoke host cellular immune responses that result in hemocytic encap... more Endoparasitoids of arthropods evoke host cellular immune responses that result in hemocytic encapsulation of the endoparasitoid, unless these responses are disrupted by the parasite. Our interest has focused on mutualistic viruses found in some hymenopteran endoparasitoids that disrupt hemocyte function and prevent encapsulation. Specifically, the Campoletis sonorensis polydnavirus interacts with wasp factors to suppress immunity via expression of intracellular and secreted viral proteins. To study the roles of specific parasitizationassociated factors on immunocyte morphology, fluorescence microscopy was used to visualize the actin cytoskeleton in infected and uninfected cells, or after treatment with C. sonorensis ovarian proteins or plasma from infected larvae. The titer and distribution of Fand G-actin were altered in hemocytes from parasitized insects relative to control cells, with plasma from parasitized larvae having an intermediate effect. This suggests that intracellular and secreted factors contribute to suppression of cellular immune responses in C. sonorensis.
Monday, 15 November 2004 D0175. Transcriptional profile of the Campoletis sonorensis Ichnovirus v... more Monday, 15 November 2004 D0175. Transcriptional profile of the Campoletis sonorensis Ichnovirus vinnexin gene family. Yayi Kusumah, [email protected] and Matthew Turnbull, [email protected]. Clemson University ...
Virology, 2006
Symbionts often exhibit significant reductions in genome complexity while pathogens often exhibit... more Symbionts often exhibit significant reductions in genome complexity while pathogens often exhibit increased complexity through acquisition and diversification of virulence determinants. A few organisms have evolved complex life cycles in which they interact as symbionts with one host and pathogens with another. How the predicted and opposing influences of symbiosis and pathogenesis affect genome evolution in such instances, however, is unclear. The Polydnaviridae is a family of double-stranded (ds) DNA viruses associated with parasitoid wasps that parasitize other insects. Polydnaviruses (PDVs) only replicate in wasps but infect and cause severe disease in parasitized hosts. This disease is essential for survival of the parasitoid's offspring. Thus, a true mutualism exists between PDVs and wasps as viral transmission depends on parasitoid survival and parasitoid survival depends on viral infection of the wasp's host. To investigate how life cycle and ancestry affect PDVs, we compared the genomes of Campoletis sonorensis ichnovirus (CsIV) and Microplitis demolitor bracovirus (MdBV). CsIV and MdBV have no direct common ancestor, yet their encapsidated genomes share several features including segmentation, diversification of virulence genes into families, and the absence of genes required for replication. In contrast, CsIV and MdBV share few genes expressed in parasitized hosts. We conclude that the similar organizational features of PDV genomes reflect their shared life cycle but that PDVs associated with ichneumonid and braconid wasps have likely evolved different strategies to cause disease in the wasp's host and promote parasitoid survival. D
Advances in Virus Research, 2002
... Nerissa Marziano , Department of Biosciences, University of Kent, Canterbury, Kent, United Ki... more ... Nerissa Marziano , Department of Biosciences, University of Kent, Canterbury, Kent, United Kingdom. Matthew Turnbull , Department of Biological Sciences and Entomology, Soils, and Plant Sciences, Clemson University, Clemson, SC. ...
Journal of insect behavior, 2002
In assays investigating the abdominal sternal secretion of the cockroach Eurycotis floridana, it ... more In assays investigating the abdominal sternal secretion of the cockroach Eurycotis floridana, it was determined that the secretion provides an effective deterrent against potential predators. Analysis of grooming patterns of Peromyscus leucopus mice revealed significant increases in mouth grooming and loss of coordination following exposure to E. floridana secretion. Mouse-cockroach interactions also changed following exposure of the mouse to the spray, as the mouse incited fewer interactions and more frequently struck with its forepaws than with its mouth. Monomorium sp. and Camponotus sp. ants also were repelled by the secretion, and Periplaneta americana were significantly irritated by the application of E. floridana secretion. The secretion is able to deter without physical contact, presumably via noxious volatiles. Eurycotis floridana is capable of accurately aiming the discharge as well as ejecting it several times the length of its body. It also was found that E. floridana exhibits autotoxic responses following contact with the secretion of conspecifics.
Journal of Virology, 2011
Polydnaviruses are double-stranded DNA viruses associated with some subfamilies of ichneumonoid p... more Polydnaviruses are double-stranded DNA viruses associated with some subfamilies of ichneumonoid parasitoid wasps. Polydnavirus virions are delivered during wasp parasitization of a host, and virus gene expression in the host induces alterations of host physiology. Infection of susceptible host caterpillars by the polydnavirus Campoletis sonorensis ichnovirus (CsIV) leads to expression of virus genes, resulting in immune and developmental disruptions. CsIV carries four homologues of insect gap junction genes (innexins) termed vinnexins, which are expressed in multiple tissues of infected caterpillars. Previously, we demonstrated that two of these, VinnexinD and VinnexinG, form functional gap junctions in paired Xenopus oocytes. Here we show that VinnexinQ1 and VinnexinQ2, likewise, form junctions in this heterologous system. Moreover, we demonstrate that the vinnexins interact differentially with the Innexin2 orthologue of an ichnovirus host, Spodoptera frugiperda. Cell pairs coexpressing a vinnexin and Innexin2 or pairs in which one cell expresses a vinnexin and the neighboring cell Innexin2 assemble functional junctions with properties that differ from those of junctions composed of Innexin2 alone. These data suggest that altered gap junctional intercellular communication may underlie certain cellular pathologies associated with ichnovirus infection of caterpillar hosts.
Immunogenetics, 2003
During parasitization of their hosts some insect parasitoids deliver resident viruses which encod... more During parasitization of their hosts some insect parasitoids deliver resident viruses which encode genes that must be expressed in the host for successful parasitization. Among these viruses the Campoletis sonorensis Ichnovirus has been well studied and encodes a cys-motif gene family implicated in disruption of host immunity and other physiological systems. Members of this gene family encode one or more intercystine-knot structural motifs in which the non-cysteine residues of the motif are variable. We analyzed patterns of synonymous and non-synonymous substitution within the cys-motif to investigate the evolution of this gene family and the likelihood of virus-host gene coevolution. Maximum likelihood techniques suggest positive selection acts on 8 of 51 codons in the aligned cysteine-rich region. Although the detected positive selection was not strong, it likely contributes to the diversification of this gene family. Comparison of selection pressure relative to tertiary structure of the VHv1.1 cys-motif protein suggests that the hypervariable sites are exposed. Furthermore, invariant residues in the motif exhibit a region-specific pattern of codon bias, suggesting there are unusual mechanisms of effecting selection pressure at work in this system, though the mechanism has yet to be studied. The positive selection and duplication of both the gene family and the cys-motif implies either selection is driving the molecular radiation of immune suppressive genes toward novel hosts, or molecular coevolution with host targets.
Florida Entomologist, 2010
Aquatic macroinvertebrates play important roles in freshwater ecosystems. The larvae of the vecto... more Aquatic macroinvertebrates play important roles in freshwater ecosystems. The larvae of the vector mosquito Culex quinquefasciatus Say (Diptera: Culicidae) primarily reside in standing water rich in organic matter; these conditions are also suited for growth of microbial biofilms. As microbes serve as a food source for larvae, the study of interactions between microbial biofilms and C. quinquefasciatus can aid in understanding the routes by which aquatic larvae can acquire pathogens, and the role such larvae may play in environmental persistence of microorganisms. Studies in butterflies, nematodes, and ticks have described interactions with bacteria acquired by the oral route, including arthropods that play a role in dissemination of bacteria on beet plants. In pursuit of these goals, this manuscript describes a new protocol for investigating larval mosquito feeding on microbial biofilms. Fluorescent microscopy and GFP expressing bacterial strains were used to show larval acquisition and midgut localization of bacteria from both planktonic and biofilm sources. PCR testing for the GFP plasmid confirmed presence of the test strain in fed larvae. The results of microscopy and PCR assays demonstrate that Culex quinquefasciatus larvae will feed on microbial biofilms in a laboratory environment. The efficiency of studying microbial fate through common microscopic and molecular techniques, in combination with an easily maintained vector insect colony, means this approach can be used to investigate a multitude of research questions relating to microbial effects on larval physiology, fitness, and conditioning.
FEMS Microbiology Ecology, 2011
Francisella tularensis is an environmental bacterium capable of infecting a wide spectrum of spec... more Francisella tularensis is an environmental bacterium capable of infecting a wide spectrum of species from mammals and birds to reptiles. It has been demonstrated that F. tularensis can invade and survive within protozoa, but an association with aquatic insects has not been thoroughly investigated. We examined the interaction of F. tularensis LVS biofilms and Culex quinquefasciatus larvae to determine the effects on larvae and adults. Our results demonstrate that F. tularensis LVS can form and persist as biofilms in natural water and that the mosquito larvae of C. quinquefasciatus readily feed on biofilm and planktonic forms of F. tularensis LVS. Larvae raised in both bacteria-only cultures suffered significant delays in pupation. Adults resulting from larvae continuously exposed to the bacteria had significantly reduced wing lengths in males and fecundity of both sexes. The bacteria may be exerting these effects through localization and persistence within the midgut and Malpighian tubule cells of the larvae. The study of oral acquisition of pathogens by insect larvae can significantly contribute to the study of environmental persistence of pathogens. We show that oral uptake of F. tularensis LVS by C. quinquefasciatus larvae results in not only larval effects but also has effects on adult mosquitoes. These effects are important in understanding both the ecology of tularemia as well as bacterial interactions with aquatic invertebrates.
FEBS Letters, 2014
The past decade has seen significant advances in the field of innexin biology, particularly in th... more The past decade has seen significant advances in the field of innexin biology, particularly in the model invertebrate organisms, the nematode Caenorhabditis elegans and the fly Drosophila melanogaster. However, advances in genomics and functional techniques during this same period are ushering in a period of comparative innexin biology. Insects are the most diverse metazoan taxa in terms of species number, as well as in developmental, physiological, and morphological processes. Combined with genomics data, the study of innexins should rapidly advance. In this review, we consider the current state of knowledge regarding innexins in insects, focusing on innexin diversity, both evolutionary and functional. We also consider an unusual set of innexins, known as vinnexins, that have been isolated from mutualistic viruses of some parasitoid wasps. We conclude with a call to study insect innexins from a broader, evolutionary perspective. Knowledge derived from such comparative studies will offer significant insight into developmental and evolutionary physiology, as well as specific functional processes in a taxon that has huge biomedical and ecological impact on humans.
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Papers by Matthew W Turnbull